The knife attack occurred near or adjacent to the Notre-Dame church in Nice at 09:00 on Thursday.
Three people were killed and several are injured.
The perpetrator was defused by police and taken to hospital with serious injuries.
President Emmanuel Macron calls the incident an Islamist terrorist attack and has raised the level of terrorist threats in the country to the highest possible.
At 21.00, anti-terror prosecutor Jean-Francois Ricard will hold a press conference. SVT News broadcasts live.